Medical instruments, particularly surgical instruments, are typically sterilized prior to use using steam or other sterilizing/disinfecting gases or liquids. A traditional sterilization process uses steam under pressure. Alternative sterilization processes use ethylene oxide or hydrogen peroxide in vapor form as the sterilant.
The use of hydrogen peroxide and other chemical vapor phase sterilization techniques typically involve operating temperatures well below those associated with steam sterilization. These “low temperature” technologies generally operate at temperatures below about 80° C., and often below about 65° C. For hydrogen peroxide sterilization, the sterilized goods are typically available for use shortly after the completion of the sterilization cycle. This is because the decomposition products (e.g., water and oxygen) are nontoxic. The potency of the hydrogen peroxide may be augmented by the presence of electrical energy in the form of an ionizing plasma field.
An alternative sterilization process uses a liquid phase peracetic acid solution. Such sterilization processes may be performed in a sterilization chamber. During a typical sterilization cycle, an article to be sterilized is exposed to a sterilization solution containing, for example, about 2000 parts per million (ppm) to 2500 ppm of peracetic acid. The article is exposed to the solution for a sufficient time at a sufficiently high temperature, e.g., 50° C.–60° C., for the sterilization to be effective.
Sterilization indicators are used to monitor whether a sterilization process has been performed. Sterilization indicators typically include an indicator composition, carried on a substrate, that changes color during the sterilization process. Conventional indicators for hydrogen peroxide, however, often fade upon exposure to light. Thus, there is still a need for suitable indicators that include color change compositions for indicating the sterilization of articles using hydrogen peroxide or peracetic acid.